Well, c31 and c29 haven't quite leveled out yet (previous graph).
I have found this to be a good indicator:

Roughly a 1/10 G/s c31/c29 factor, I get 40 G/s on c29, and about 4 G/s on c31.
BTW, went through their support yesterday (Zen desk), and got an answer and solution instantly (email had not arrived).
I'm not shilling about sparkpool, just saying.
Also, got almost 3 Grin with c31 instead of almost 2 (that would have got) with c29.
Was briefly thinking of leaving my Vega64's on c31 and Minerbabe, and flipping the 1080ti's to Bminer 14. Maybe tomorrow.